The decongestant in most cold tablets doesn't work. Here's what does.

What just happened

With winter respiratory illness peaking across Australia, SBS News has revisited a question that resolved overseas in August 2024 but hasn’t fully filtered through to how Australians shop for cold relief: does the decongestant in most cold and flu tablets actually work?

The answer — according to a US FDA advisory panel ruling from August 2024 — is no. Not when taken by mouth. Oral phenylephrine, the active ingredient in most supermarket cold and flu preparations, does not reach nasal tissue at concentrations high enough to reduce congestion. The FDA concluded after reviewing the full body of evidence that phenylephrine taken orally is no more effective than placebo at the doses used in over-the-counter products. Australian medicines experts, including pharmacists and clinical pharmacologists, have agreed with that finding.

The ingredient hasn’t been recalled. It isn’t unsafe. But it also doesn’t do the job it’s on the packet to do.

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The both-and

How phenylephrine ended up in everything

The short history here matters. Pseudoephedrine — the decongestant that does work — was the main active ingredient in cold and flu tablets for decades. In the mid-2000s, Australian states and territories progressively moved pseudoephedrine behind the pharmacy counter, where it can only be sold with ID and is subject to real-time monitoring under Project STOP, a national database that tracks purchases to prevent diversion into methamphetamine production.

Pharmaceutical manufacturers replaced pseudoephedrine in their supermarket formulations with phenylephrine, which carries no such restrictions. Products with ‘PE’ in the name — Sudafed PE, Codral PE, Lemsip Max — are the phenylephrine versions. The original formulations, still available behind the pharmacy counter, retained pseudoephedrine.

The problem is that phenylephrine doesn’t absorb well from the gut into systemic circulation. It’s broken down extensively in the intestinal wall before it gets anywhere near nasal blood vessels. The dose that reaches its target is too small to have a decongestant effect. This was suspected in the pharmacology literature for years before the FDA formally concluded in 2024 that the evidence didn’t support the ingredient’s effectiveness by the oral route.

What actually works for nasal congestion

Healthdirect summarises the evidence-based options clearly. Two categories have good evidence:

Pseudoephedrine (oral): Still the most effective oral decongestant available. Sold behind the pharmacy counter at all Australian pharmacies. You’ll need to show ID and have your details recorded in Project STOP. The pharmacist can dispense it without a prescription but will ask why you want it. For most healthy adults with an uncomplicated cold, this is the most convenient option when meaningful nasal relief matters.

Topical nasal sprays: Oxymetazoline (found in Dimetapp Nasal Spray, Vicks Sinex, Otrivin Extra) and xylometazoline (Otrivin) work directly on nasal blood vessels. They act within minutes and are highly effective. The important limit is three to five days of use. Beyond that, the nasal lining can become dependent on the vasoconstricting effect, and congestion rebounds when the spray wears off — a condition called rhinitis medicamentosa, or rebound congestion. Used correctly (short courses only), nasal sprays are the fastest-acting option.

Saline nasal rinses — available as sprays or as neti pot preparations — are not decongestants, but they do help clear mucus and may reduce duration of symptoms. They carry no usage-day limits and are safe in pregnancy and for children.

Who should be cautious with any decongestant

Decongestants — oral and topical — constrict blood vessels. That mechanism is why they reduce nasal swelling. It’s also why they carry cautions for people with high blood pressure, heart disease, an overactive thyroid, or enlarged prostate. Pregnancy is another situation where decongestant use should be discussed with a GP or pharmacist before starting.

For people in these groups, saline rinses and steam inhalation are the safer first options. A pharmacist can help identify which, if any, decongestant is appropriate.

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My two cents

This is one of those situations where the product on the shelf is legal, marketed in good faith under old regulatory approvals, and genuinely not doing what people think it’s doing. Phenylephrine isn’t being pulled. No recall is coming. It will continue to appear on pharmacy and supermarket shelves until manufacturers reformulate or regulators act — and the Australian regulator (the TGA) has not yet made a formal ruling equivalent to the FDA’s.

In the meantime, the practical knowledge is simple:

• If you want oral relief from nasal congestion, ask the pharmacist for the pseudoephedrine version — original Sudafed, original Codral, or a generic equivalent. Have your ID ready.
• If you want fast relief and don’t want to visit a pharmacy counter, a nasal spray (oxymetazoline or xylometazoline) from the open shelf will work — but respect the three-to-five day limit.
• If you or someone in your household should avoid vasoconstrictors — high blood pressure, heart disease, pregnancy — saline rinse first, and check with a pharmacist before anything else.

The ‘PE’ label on a cold tablet is, at this point, a signal that the product has the ingredient that doesn’t work. That’s not common knowledge yet. Now it is.

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Verdict: yes — worth knowing about.

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Sources cited

1. SBS News — Feeling congested this winter? A common medicinal ingredient might not be helping (2026). https://www.sbs.com.au/news/article/feeling-congested-this-winter-a-common-medicinal-ingredient-might-not-be-helping/kdyydmiy4
2. Healthdirect — Decongestants. https://www.healthdirect.gov.au/decongestants